Method of manufacturing glass panel and glasspanel manufactured by the method

ABSTRACT

A glass panel (P) including a pair of glass sheets ( 1 A), ( 1 B) disposed in a spaced relationship with each other with forming a gap (V) therebetween, characterized in that peripheral edges of the glass sheets ( 1 A), ( 1 B) are bonded directly by a single metal material ( 3 ) for sealing the gap (V) hermetically.

TECHNICAL FIELD

The present invention relates to a glass panel including a pair of glasssheets with a gap being formed between opposing faces of the sheets andthe gap being hermetically sealed by peripheral edges of the glasssheets. The invention relates also to a method of manufacturing suchglass panel.

BACKGROUND ART

For a double glazing or glass panel having peripheral edge thereofsealed, it has been conventionally proposed to bond and seal the entireperipheral edges of the opposing faces of the pair of glass sheets byusing metal material such as solder. However, the glass sheets generallydo not directly wet with the molten metal material. For this reason, ithas been a conventional practice to form, in advance, a metallic coatingfilm having good wettability with the solder at bonding portions on theopposing faces of the pair of glass sheets and then to bond the solderwith the glass sheets via such metallic coating film. As such solderingmethod and the manufacturing method of a bonded assembly of glass sheetsutilizing the soldering method, various types of method are known.

For instance, Japanese laid-open patent publication (Kokai) No. Sho.53-145833 discloses a multiple glazing including two or more glasssheets having metallized edge portions, metallized with e.g. coppercoating, thereof soldered.

Further, Japanese laid-open patent publication (Kokai) No. Sho. 54-81324discloses art of assembling respective components for forming anenclosure in hermetic manner, with at least one of the components beingglass. In this, there is disclosed a method of bonding, by means ofsolder, portions to be bonded which portions have been metallized inadvance by e.g. vapor evaporation process.

Still further, Japanese patent publication (Kokoku) No. Hei. 1-58065discloses, as a high-airtight soldering multiple layer, a multiple layerconsisting of a bottom layer, a middle layer and a top layer, whichcomprises Cu and NiCr films or the like formed on a surface of a basematerial such as glass.

Further, as the soldering methods, such methods have been attempted asinserting a metal element as an intermediate element between glasssubstrates having metallic coating films at bonding portions thereof andthen bonding these glass substrates and the metallic element by means ofsolder or as coating solder in advance at the peripheral edges of theglass substrates having metallic coatings and then heating underpressure the substrates so as to bond them together. In either case, thesolder employed contains a large amount of lead.

However, with those methods disclosed by the prior art, it has beendifficult to obtain hermetically sealed glass panels with goodreproducibility. Namely, with such glass panels soldered via themetallic coating films formed at the bonding portions of the glasssheets, sufficient mechanical strength can be obtained, but they areunsatisfactory in the respect of the hermetic seal. This is because ofthe presence of different material interfaces not only between therespective glass sheets and the solder, but also between the solder andthe metal coating film as well as between the metal coating film andeach glass sheet. The presence of such interfaces is verydisadvantageous for hermetic seal.

Further, in actual manufacturing process, there tend to occurirregularities in the fused condition of the solder at the time ofbonding. Because of this, it sometimes happens that the base solderingmetallic coating film may be dissolved in the solder completely, thusresulting in insufficient bonding between the solder and the respectiveglass sheets or that oxidation may develop before the solder can wet theglass sheets, thus leading to deterioration in the hermetic seal.

Also, in the case of the method of bonding glass sheets pre-coated withsolder, it is difficult to completely eliminate, at the time of bonding,any oxide dross present originally on the solder coating surface so asto preclude even microscopic inclusions thereon. For this reason, thebonding would be poor in terms of hermetic seal and unsatisfactoryespecially as vacuum seal.

In addition to the above, if solder with high lead content is employed,the lead may be eluted from the sealed portion of the glass panel whenthe panel is exposed under such environment as exposure to acid rain, sothat there is the possibility of giving adverse effect to theenvironments.

As described above, the prior art has taught no specific requirementsregarding the bonding condition between the glass sheets and the metalrequired for providing hermetic seal. In particular, it has beenpractically difficult to manufacture a relatively large glass panel suchas one for use in a windowpane in a building. The present invention hasbeen made to solve such problems. Its object is to provide a glass panelincluding a pair of glass sheets having their peripheral edges sealed inhermetic manner. Another object is provide a glass panel which is freefrom elution of lead, thus giving no adverse effect to the environments.

DISCLOSURE OF THE INVENTION

The characterizing features of a glass panel and its manufacturingmethod are as follows.

A glass panel, as shown in FIGS. 2 and 3, includes a pair of glasssheets disposed in a spaced relationship with each other with forming agap therebetween, peripheral edges of the glass sheets being bondeddirectly by a single metal material for sealing the gap hermetically,characterized in that the panel satisfies the following relationship:

100≦T _(L)≦(T _(S)−100)

where T_(L) is the liquidus temperature (° C.) of the metal material andT_(S) is the strain point (° C.) of the glass sheets.

As is the case with the prior art described hereinbefore, when solderingmetallic coating films are formed in advance on the peripheral edge ofthe pair of glass sheet and then metal material is applied between thesemetallic coating films, microscopic gaps which can serve as passages forgas molecules tend to be formed at such different material interfacesbetween the glass sheet surface and the metallic coating film andbetween the metallic coating film and the metal material.

On the other hand, according to the above construction of the invention,the bonding to the glass sheets employs a single metal material withoutusing any soldering metallic film coatings. Therefore, it is possible tomaintain air-tightness at the peripheral edges of the glass sheets.

In the above, what is referred to as “direct bonding between the glasssheets and the metal material” as used in the concept of the presentinvention means that the only different material interface present isthe interface between each glass sheet and the metal material. And, theterm: “single metal material” refers to a single element metal or analloy having a certain composition to be used alone between the pair ofglass sheets. For instance, sealing by using two or more kinds of solderhaving different compositions from each other is obviously excluded fromthe scope of the invention. Also, a condition of any other substancethan the metal material being present at the bonding portion is contraryto the concept of the invention. Namely, when solder-coated glass sheetsare bonded by heating with each other, the inclusions originated fromthe oxides formed on the raw solder material is contained within thesolder, tending to result in reduction in the air-tightness. Further,the residual substance such as flux commonly employed for preventingoxidation of solder must not be present at the bonding portions since itdeteriorates the air-tightness. That is to say, the conventional methodinvolving the preliminary formation of the metal coating film for solderwelding and a glass panel obtained by such method are out of the scopeof the present invention.

With the bonding technique of coating the glass sheet surfaces withsolder in advance and then boding the sheets face to face, the oxides oneach solder surface will remain to form a different material interface.Therefore, such technique too is out of the scope of the presentinvention. Namely, the method taught by the prior art is contrary to theconcept of the present invention.

As described hereinbefore, the present invention is characterized inthat the air-tightness is provided by direct bonding between the glasssheet and the single metal material. However, the scope of the presentinvention does not exclude presence of other metal material, inorganicmaterial or organic material at or in the vicinity of the bondingportions. That is to say, it is possible to dispose in advance a wireelement, powder or the like formed of other metal material than thesealing metal material at the bonding portions of the glass sheets andthen to charge the sealing metal material at these bonding portions sothat a certain component contained in the wire element, powder materialor the like may dissolve into the sealing metal material for improvingthe bonding strength or to coat bonding portions with an inorganicmaterial, organic material or the like for protection from theenvironment. These modified constructions are not contrary to theconcept of the invention.

Then, the glass panel according to the invention is characterized inthat the panel satisfies the following relationship:

100≦T _(L)≦(T _(S)−100)

where T_(L) is the liquidus temperature (° C.) of the metal material andT_(S) is the strain point (° C.) of the glass sheets.

Here, the term: “liquidus temperature T_(L) of the metal material”refers to the temperature at which the metal completely becomes a liquidphase when heated from a lower temperature. Such temperature can bedetermined by the differential thermal analysis for instance.

Further, the term: “strain point T_(S) of the glass sheet” refers to thetemperature at which the glass has a viscosity of 4×10¹⁴ (dPa.s) (4×10¹⁴poise).

In general, the metal material is to be bonded with a glass sheet whilethe metal material is in its molten condition. Therefore, in order toavoid deformation of the glass sheet, it is desired that the liquidustemperature T_(L) (° C.) be lower than the strain temperature T_(S) (°C.) of the glass sheet to be bonded. With this, it becomes possible toeffect the bonding within a temperature range where the deformation ofthe glass sheet is small. Further, in order to minimize the stressresultant from a difference in thermal expansion between the glass sheetand the metal material which stress can lead to breakage, it is desiredthat the bonding be effected at a lowest possible temperature. As a ruleof thumb, it is preferred that T_(L) be lower than T_(S) by 100° C. ormore. In its daily use, the glass panel can be heated to a considerablyhigh temperature when exposed to a strong sunbeams during summer. Insuch case, if T_(L) is too low, the strength will be reduced. For thisreason, it is preferred that T_(L) be higher than 100° C. It is morepreferred that T_(L) be higher than 150° C.

To summarize the above, the preferred relationship between the liquidustemperature T_(L) (° C.) of the sealing metal material and the strainpoint T_(S) (° C.) of the glass sheets to be bonded is:100≦T_(L)≦(T_(S)−100). Then, the liquidus temperature of the metalmaterial is adjusted so as to satisfy the above relationship byappropriate adjustment of the ratio of its components.

The glass panel according to a preferred embodiment is characterized inthat the lead content in the metal material is below 0.1 wt. %.

With this construction, even when the glass panel is exposed to a severeenvironment such as exposure to acid rain, there occurs no elution oflead, thus providing no adverse effect to the environment.

The glass panel according to a preferred embodiment is characterized inthat the metal material contains two or more kinds of componentsselected from a group consisting of Sn, Zn, Al, Si and Ti.

With this construction, the contained components and oxygen present onthe glass sheet surfaces will be bonded to each other to improve thebonding strength.

As the metal material to be used at the bonding portions according tothe present invention, solder having the above-defined components andrange of composition may be cited. More preferred range of compositionand the reasons thereof are as follows. In the following discussion, thecompositions and component ratios are represented as weight %.

Sn is non-toxic and provides the function of providing wettability tothe object to be bonded.

Zn provides a bonding force to oxide materials such as glass, ceramics,etc. If the addition amount of Zn is too large, there occurs increasingtendency of brittleness of the solder, hence not desirable for actualuse. The preferred range of its addition amount is 0.5˜10%.

The binary system of Sn and Zn is an eutectic system. With eutecticcomposition, the composition can easily become an alloy having finestructure by cooling from its molten condition. The eutectic pointcorresponds to the composition of Sn 91% and Zn 9%. At its eutectictemperature 198° C., a liquid phase and two solid phases of Sn and Zncoexist. This eutectic composition can easily become a fine metalstructure by cooling and solidifying, as described above. So that, thiscomposition is flexible, thus being advantageous for relaxing stressgenerated in the course of the bonding operation with the glass sheets,thus improving the bonding strength. Accordingly, it is preferred thatthe solder contain Sn and Zn in a ratio approximating such eutecticcomposition thereof. In particular, it is preferred that Zn be presentat 8 to 10% relative to the sum of Sn and Zn.

Al is an element which can be oxidized very easily, but it provides theadvantageous effect of being readily bonded with an oxide. Such effectwill be low if the addition amount of Al is below 0.001%. Whereas, if itexceeds 3.0%, this will result in increase in the hardness of the solderper se. Hence, it becomes difficult to ensure heat-cycle resistance andthe melting point will rise to deteriorate the workability. Then, thepreferred range of its addition amount is 0.001 to 1.0%.

Si is also an element which can be oxidized very easily, but it providesthe advantageous effect of being readily bonded with an oxide. With asmall addition amount, it will be effective for rendering the metalstructure finer during the cooling/solidifying process, so as toincrease the flexibility of the solder. This effect will be low if theaddition amount of Si is below 0.001%. Whereas, if it exceeds 3.0%, thiswill result in increase in the hardness of the solder per se. Hence, itbecomes difficult to ensure heat-cycle resistance and the melting pointwill rise to deteriorate the workability. Then, the preferred range ofits addition amount is 0.001 to 1.0%.

Ti is also an element which can be oxidized very easily, but it providesthe advantageous effect of being readily bonded with an oxide. Further,since Ti has a large oxygen solubility, it is effective for causing thesolder to contain oxygen. That is, with Ti, it becomes possible for thesolder to contain oxygen in the form of Ti—O, without elution of oxides.And, this oxygen promotes the formation of bonding to the glass, as willbe detailed later. This effect will be low if the addition amount of Tiis below 0.001%. Whereas, if it exceeds 3.0%, this will result inincrease in the hardness of the solder per se. Hence, it becomesdifficult to ensure heat-cycle resistance and the melting point willrise to deteriorate the workability. Then, the preferred range of itsaddition amount is 0.001 to 1.0%.

The glass panel according to a preferred embodiment is characterized inthat the metal material contains O (oxygen) in the range from 0.0001 to1.5 wt. %.

For instance, by the presence of oxygen in the dissolved form within themetal material, it is possible to promote the formation of the bondingat the interface between the glass sheet and the metal material. Inorder to cause the metal material to contain oxygen, this is possible byeither or both of melting and producing the metal material in anoxygen-containing atmosphere and carrying out the bonding with the glasssheets in an oxygen-containing atmosphere.

Oxygen is a component which promotes bonding between the metal materialand the glass. With oxygen being present in an dissolved form within themetal material, at the interface between the glass and the metalmaterial, the transition from the oxide bonding to the metal bonding canoccur smoothly, thereby to reinforce the bonding interface. This effectwill be low if the oxygen concentration is too low. On the other hand,if the concentration is too high, this will tend to invite elution ofoxide in the metal material. Then, the oxygen concentration shouldpreferably be 0.0001% or higher, more preferably 0.001% or higher, andyet preferably should range between 0.001 and 1.5%. The preparation ofsuch oxygen-containing metal material is possible by melting the metalmaterial in an oxygen-containing atmosphere, e.g. an ambient atmosphere.And, its oxygen content can be increased or decreased by appropriatelyadjusting the melting temperature, period, etc. Further, even if themetal material does not contain oxygen before it is used for the bondingoperation, the metal material after the bonding operation may contain apreferred concentration of oxygen by appropriately adjusting theatmosphere in which the bonding is carried out. In such case,substantially same high bonding strength may be obtained as use of theoxygen-containing metal material.

The glass panel according to a preferred embodiment as illustrated inFIGS. 4-8, is characterized in that the pair of glass sheets havedifferent dimensions so that one glass sheet is disposed in oppositionto the other glass sheet with the one sheet projecting at a peripheraledge thereof by a width of 1 to 10 mm from each peripheral edge of theother sheet, with the metal material being charged from the projectingportion of the one glass sheet into the gap between the glass sheets.

With this construction, not only the gap but also the end faces of theglass sheets can contribute to the bonding, whereby the bonding strengthmay be improved.

The glass panel according to a preferred embodiment is characterized inthat the gap is sealed to keep a depressurized condition.

With this construction, it is possible to reduce the thermalconductance, whereby a glass panel having superior heat insulatingperformance may be obtained.

A method of manufacturing a glass panel according to a preferredembodiment as illustrated in FIG. 1, is characterized by the steps of:disposing spacers between the pair of glass sheets to form a gaptherebetween; charging a molten single metal material to the peripheraledges of the glass sheets, the metal material satisfying the followingrelationship:

100≦T _(L)≦(T _(S)−100)

where T_(L) is the liquidus temperature (° C.) of the metal material andT_(S) is the strain point (° C.) of the glass sheets; and directlybonding the glass sheets and the metal material together so as to sealthe gap hermetically.

With the conventional method, e.g. a metal coating film for bonding withmolten solder is provided on the surface of each glass sheet for sealingbond. In such case, a number of different material interfaces existbetween the glass sheet surface and the metal coating film, between themetal coating film and the solder, etc.

On the other hand, in the case of the invention's method in which asingle metal material is charged to the peripheral edges of the glasssheets, only two different material interfaces are present, so that itsnumber can be minimized. Accordingly, microscopic gaps will hardly beformed at the different material interfaces, whereby the reliability ofthe air-tightness at the peripheral edges of the glass sheets may beimproved.

In the above, in “charging the molten metal material to the peripheraledges of the glass sheets”, it is important that the glass sheets andthe metal material be bonded directly with each other. Any oxidegenerated when the molten metal material comes into contact with anoxygen-containing atmosphere is present on the bonding interface, thiswill result in reduction in bonding strength, making it difficult forthe assembly to withstand its evacuated air-tightness as well. For thisreason, such oxides must be eliminated as much as possible.

And, in this method, the method employs the metal material whichsatisfies the following relationship:

100≦T _(L)≦(T _(S)−100)

where T_(L) is the liquidus temperature (° C.) of the metal material andT_(S) is the strain point (° C.) of the glass sheets. Then, in bondingthe molten metal material with the glass sheets, it is possible toprevent deformation in the glass sheets. Further, by minimizing thestress occurring from a difference in thermal expansion between theglass sheets and the metal material, it is possible to prevent breakageof the glass sheets also.

The method of manufacturing a glass panel according to a preferredembodiment is characterized by the steps of: heating and maintaining thepair of glass sheets at a temperature below the liquidus temperature ofthe metal material, the molten metal material having a portion cominginto contact with an atmosphere and a further portion not coming intocontact with the atmosphere before the metal material is charged intothe gap between the glass sheets; and charging into the gap at theperipheral edge of the glass sheets only the portion of the metalmaterial which did not come into contact with the atmosphere, whilepreventing the portion which came into contact with the atmosphere frombeing charged into the gap.

With the above method, by heating the glass sheets to a temperaturebelow the liquidus temperature of the metal material, the wettability ofthe glass sheets may be improved for facilitating the charging operationof the metal material.

Further, the reason for the prevention of the portion which came intocontact with the atmosphere from being charged into the gap is asfollows.

Namely, if the metal material contains a component having a largeaffinity relative to oxygen, even a small amount of oxygen in theatmosphere can cause development of oxidation in the metal material. Forthis reason, it will become necessary in general to carry out thebonding operation with the glass sheets in an inert atmosphere or undera depressurized condition. In this, according to the invention's method,only the inner portion of the metal material coated with oxides iscaused to permeate into the gap, thereby to prevent the oxides formed onthe surface thereof from entering the bonding portion.

The method of manufacturing a glass panel according to a preferredembodiment as shown in e.g. FIGS. 11 and 12, is characterized that thestep of charging the molten metal material into the gap between theglass sheets employs a guide for guiding the metal material to the gap,at least a portion of the guide being inserted into the gap.

In the above, the “guide” refers to a member adapted for guiding themolten metal material from an outlet of its feeding device to the gapbetween the glass sheets. The molten metal material is guided to thetarget position by its wetting with the guide as well as by therestriction of its flow by the shape of the guide.

With the method described above, as the guide is provided, theintroduction of the metal material into the gap, which tends to bedifficult in the case of a narrow gap, can be promoted and facilitated,and the introducing speed may be increased, so that the above-describeddirect bonding between the metal material and the glass sheets may beformed easily.

The method of manufacturing a glass panel according to a preferredembodiment, as shown in e.g. FIGS. 11 and 12, is characterized in thatthe guide is a plate-like or bar-like guide.

With the guide having such shape as above, by appropriately setting e.g.the thickness of its plate-like portion or the diameter of its bar-likeportion, this guide may be inserted into the gap, regardless of the sizeof this gap between the pair of glass sheets. Accordingly, the chargingoperation of the metal material may be carried out in a reliable manner.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in e.g. FIGS. 13 through 16, is characterized inthat the method employs a stimulus conducting member for physicallystimulating the interface between the molten metal material and theglass sheet surface so as to promote the direct bonding therebetween, atleast a portion of the stimulus conducting member being inserted intothe gap.

In the above, the “stimulus conducting member” refers to a membercapable of conducting a physical stimulus to the molten metal materialof the gap. By applying a physical stimulus to the molten metalmaterial, any oxides etc. which can interfere with the direct bonding atthe interface between the metal material and the glass can be eliminatedforcefully, so that a more firm and dense bonding interface suitable forthe hermetic sealing may be obtained.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in e.g. FIGS. 13 through 16, is characterized inthat the stimulus conducting member is a plate-like or bar-like member.

As described above in connection with a preferred embodiment, with thestimulus conducting member having such shape as above, by appropriatelysetting e.g. the thickness of its plate-like portion or the diameter ofits bar-like portion, a portion of this member may be inserted into thegap, so that the physical stimulus for promoting the direct bonding atthe interface between the metal material charged at the gap and theglass may be applied in an efficient and effective manner.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in e.g. FIGS. 13 through 16, is characterized inthat the physical stimulus for promoting the direct bonding is providedby mechanical movement of the stimulus conducting member.

In general, the molten metal material to be charged into the gap has acertain viscosity. Then, with the method of the invention in which thestimulus conducting member inserted into the gap is mechanically moved,the metal material charged into the gap is forcibly moved, so that thephysical stimulus for promoting the direct bonding at the interface withthe glass can be applied in an efficient and effective manner.

The method of manufacturing a glass panel according to a preferredembodiment, is characterized in that unevenness is provided on a surfaceof the stimulus conducting member.

In the above “unevenness” includes grooves and projections. With thisunevenness, the interface between the molten metal material and theglass may be effectively renewed. For instance, as the friction betweenthis stimulus conducting member and the molten metal material isimproved thus further increasing the physical stimulus, the molten metalmaterial may be stirred strongly. As a result, it is possible toforcibly eliminate oxides of the metal material which would otherwisetend to remain at the interfaces.

Further, if the stimulus conducting member and the glass come intocontact with each other so that the molten metal material is chargedwhile rubbing also the surface of the glass sheet, the physical stimulusis further increased and the components of the metal material and thecomponents of the glass can come into more direct contact with eachother. So that the bonding will become stronger and denser, thuscontributing to formation of superior bonding interface therebetween.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in FIGS. 11-16, is characterized in that the guideand/or stimulus conducting member is moved along the gap.

With the above method, the peripheral edge of a glass panel having along side may be sealed easily.

Also, in the case of such movement of the stimulus conducting member,this mechanical movement of the stimulus conducting member can alsoserve as physical stimulus for promoting the direct bonding.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that the mechanical movement of thestimulus conducting member is at least either of rotation and vibration.If the mechanical movement to be applied is either rotation orvibration, this makes it easier to make the device. The, with using suchsimple device, the peripheral edge of the glass panel may be sealedreliably.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that at least one of the guide and thestimulus conducting member is made of a metal material.

If the guide or the stimulus conducting member is formed of a metalmaterial as above, a guide or stimulus conducting member having desiredstrength, corrosion resistance, etc., may be obtained easily.

Incidentally, the guide or the stimulus conducting member may be formedalternatively of ceramics etc, depending on the necessity.

The manufacturing method of a glass panel according to a preferredembodiment, is characterized in that the guide and the stimulusconducting member are provided as a single member having the functionsof both of them.

With this method, the molten metal material may be easily inserted intothe gap and also the bonding interface between the glass sheets and themolten metal material may be formed efficiently.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in FIGS. 4-8, is characterized in that the pair ofglass sheets have different dimensions from each other and one glasssheet is disposed in opposition to the other glass sheet with aperipheral edge of the former projecting from a peripheral edge of thelatter by a width of 1 mm through 10 mm, and the metal material ischarged from the projecting portion of the one glass sheet toward thegap by utilizing capillary phenomenon.

With this method, by disposing one glass sheet on the lower side, themolten metal material can be introduced into the gap via the projectingportion. Hence, the charging operation of the molten metal material maybe facilitated.

The manufacturing method of a glass panel according to a preferredembodiment, as shown in FIGS. 17 and 18, is characterized in that thepair of glass sheets are heated and maintained at a temperature belowthe liquidus temperature of the metal material and under this condition,vibration is applied to at least one of the molten metal material or theglass sheet, so as to cause the material to permeate and to be chargedinto the gap by utilizing capillary phenomenon.

That is, with the above method, the molten metal material with itswettability to the glass sheets improved by the application of vibrationthereto is caused to permeate, by its own force commonly referred to ascapillary phenomenon, into the peripheral edge to fill the gap. Withthis method, the formation of the dissimilar material interface whichwould occur with the prior art described hereinbefore can be minimized,so as to achieve a favorable condition for air-tightness. As a method ofapplying vibration, in addition to the method of placing the vibratingmember in direct contact with the molten metal material for applying orapplying the vibration to the glass sheets, it is also possible tovibrate the metal material without physical contact by means of e.g.electromagnetic induction.

Incidentally, by heating the glass sheets, the wettability between themolten metal material and the glass sheets may be improved; hence, thepermeation/charging of the metal material into the gap is promoted toimprove the reliability of the hermetic sealing.

The manufacturing method of a glass panel according to a preferredembodiment, is characterized in that the vibration includes two or morekinds of frequencies and either one or both of them is/are applied to atleast one of the metal material and the glass sheet.

The degree of the capillary phenomenon of the molten metal materialrelative to the gap is believed to vary, depending on such factors asthe temperature of the molten metal material, the size of the gap, etc.With the capillary phenomenon in general, the smaller the gap, thegreater the force which urges the liquid to enter it. On the other hand,this will reduce the cross section area of the area (inlet) throughwhich the liquid enters the gap, thus increasing the resistance at thisarea. Then, by providing two or more kinds of frequencies, it ispossible to obtain a good balance between the permeating force and theresistance at the inlet, thus allowing the capillary phenomenon to takeplace in a most efficient manner, thereby stabilizing the permeation ofthe molten metal material into the gap.

The manufacturing method of a glass panel according to a preferredembodiment, is characterized in that the two or more kinds of vibrationshaving different frequencies of either a low frequency of 1 Hz to 10 kHzor a supersonic frequency of 15 to 100 kHz.

With the above method, by applying the low frequency vibration of 1 Hzto 10 kHz, the resistance at the inlet encountered by the molten metalmaterial to permeate into the gap may be reduced, so that the materialmay permeate into the gap in an efficient manner.

Further, by applying the supersonic frequency of 15 kHz to 100 kHz, itis possible to restrict formation of the oxide coating film of the metalmaterial at the bonding interface.

Incidentally, when the frequency of the vibration to be applied is 15kHz to 100 kHz, the favorable effect can be achieved as described above.With a range over 15 kHz, the formation of oxide coating film of themetal material at the bonding interface may be restricted, so that asatisfactory performance for practical use may be obtained and thedevice may be inexpensive and easy to handle. To be more specific, themost preferred range is 15 kHz to 80 kHz.

Further, if vibration ranging between 800 kHz and 10 MHz, this will beeffective for improving the adherence between the metal material and theglass sheet, whereby even denser and stronger bonding interface may beobtained.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that the metal material has a leadcontent below 0.1 wt. %.

With this method, even when the glass panel is exposed to a severeenvironment such as acid rain, no elution of lead will occur. So that,it is possible to obtain a glass panel which does not give any adverseeffect to the environment.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that the metal material contains two ormore kinds of components selected from a group consisting of Sn, Zn, Al,Si and Ti.

With this method, the contained components and oxygen present on theglass sheet surfaces will be bonded to each other to improve the bondingstrength.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that the metal material contains O(oxygen) in the range from 0.0001 to 1.5 wt. %.

With this method, by the presence of oxygen in the dissolved form withinthe metal material, it is possible to promote the formation of thebonding at the interface between the glass sheet and the metal material.

The manufacturing method of a glass panel according to a preferredembodiment is characterized in that the gap is sealed to keep adepressurized condition.

With this method, it is possible to reduce the thermal conduction,whereby a glass panel having superior heat insulating performance may beobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a glass panel relating to a firstembodiment,

FIGS. 2 and 3 are partial section views showing a sealing portionrelating to the first embodiment,

FIGS. 4 and 5 are partial section views showing a sealing portionrelating to a second embodiment,

FIG. 6 is a partial section view showing a sealing portion relating to athird embodiment,

FIGS. 7 and 8 are partial section views showing a sealing portionrelating to a fourth embodiment,

FIGS. 9 and 10 are partial section views showing a sealing portionrelating to a fifth embodiment which is out of the scope of the presentinvention,

FIG. 11 is a section view showing an embodiment of a manufacturingmethod relating to a sixth embodiment,

FIG. 12 is a plan view showing the embodiment of a manufacturing methodrelating to the sixth embodiment,

FIG. 13 is a section view showing an embodiment of a manufacturingmethod relating to a seventh embodiment,

FIG. 14 is a plan view showing the embodiment of a manufacturing methodrelating to the seventh embodiment,

FIG. 15 is a section view showing an embodiment of a manufacturingmethod relating to an eighth embodiment,

FIG. 16 is a plan view showing the embodiment of a manufacturing methodrelating to the eighth embodiment,

FIG. 17 is a partial section view showing a sealing method relating to aninth embodiment, and

FIG. 18 is a partial section view showing a sealing method relating to atenth embodiment.

BEST MODE OF EMBODYING THE INVENTION

Next, embodiments of the present invention will be described withreference to the accompanying drawings.

(First Embodiment)

FIG. 1 is a section view showing a glass panel P including a pair ofglass sheets 1A, 1B disposed with their main surfaces in spacedopposition to each other via a plurality of pillars 2 herebetween so asto form a gap V between the glass sheets 1A, 1B, with peripheral edgesof the glass sheets 1A, 1B being bonded with a metal material 3 to sealthe gap V.

Each of the glass sheets 1A, 1B is a transparent float plate glasshaving a thickness of about 3 mm. In this embodiment shown in FIG. 1,one glass sheet 1A has outer dimensions slightly greater than the otherglass sheet 1B so that peripheral edges 5A of the former project fromperipheral edges 5B of the latter along the entire periphery thereofwhen these glass sheets 1A, 1B are disposed with their main surfacesbeing in opposition to each other.

The gap V is constructed to realize a depressurized condition (1.0×10⁻²(Pa) or lower) therein by e.g. evacuating the gap V after formation ofthis gap V between the glass sheets 1A, 1B.

As the metal material 3 to be employed at the bonding portion accordingto the invention, it is preferred that this material contains Sn, Zn,Al, Si, Ti, O, etc, as described hereinbefore.

However, in addition to the above, it is also possible to employ solder3A having components and composition range to be described next. In thefollowing description, the unit of representing the compositions andcomponent ratios is weight %.

Cu, if added, achieves distinguished effect for improving the mechanicalstrength of the solder 3A. If the addition amount of Cu exceeds 9%, thiswill raise the melting point and also result in generation of a largeamount of intermetallic compound with Sn, which in turn leads toreduction in the mechanical strength. Then, the more preferred range ofits addition amount is from 0.001% to 1.0%.

In addition to the components described above, appropriate amounts ofIn, Ag, Bi and Sb may be added also.

In not only lowers the melting point of the solder 3A, but also improvesits wettability, and softens the solder 3A itself. If the additionamount of In is below 0.1%, such effect will be low. If it exceeds 50%,on the contrary, it becomes difficult to ensure sufficient strength ofthe solder 3A itself and it also invites considerable cost increase.

Ag if added, like Cu described above, achieves a distinguished effectfor improvement of the mechanical strength of the solder 3A. If theaddition amount of Ag is below 0.1%, the effect will be too low toobtain any improvement of the mechanical strength. If it exceeds 6%,this will raise the melting point, like Cu, and also will result ingeneration of a large amount of intermetallic compound with Sn, therebyto invite reduction in the mechanical strength on the contrary. The morepreferred range of its addition amount is from 0.1% to 3.5%.

One or more kind of Bi and Sb may be added appropriately by a range of10% or less. Bi can improve the wettability of the solder 3A. Sb canimprove the appearance of the solder 3A applied and can also increasethe creep resistance. Further, other elements such as Fe, Ni, Co, Ga,Ge, P, etc, if added by a trace amount, can improve the performance ofthe solder 3A, i.e. its leadless property, the applicability of thesolder 3A, and the mechanical strength.

An example of the composition of the metal material 3 suitable for thepresent invention contains 0.001-3.0% of Ti, 0-3.0% of Al, 0-3.0% of Si,0-9.0% of Cu, 72-99.9% of Sn, 0.1-10.0% of Zn and not more than 0.1% orsubstantially zero % of Pb.

As a more preferred example of the composition of the metal material 3,it is proposed, in the composition of the above-defined ranges, that theratio of Zn relative to the sum of the Sn and Zn is from 8% to 10%.

FIGS. 2 and 3 are partial sections showing the sealed portion using themetal material 3. As shown, edges 5A, 5B of the glass sheets 1A, 1B aresuperposed in alignment with each other and under this condition, themetal material 3 is charged between opposing faces of the glass sheets1A, 1B. In this manner, in the case of the construction of FIG. 2, themetal material 3 is charged over a constant width including at least theedges 4A of the opposing faces of the glass sheets 1A, 1B.

For maintaining the air-tightness at the peripheral edge, it isimportant that the metal material 3 be formed from the edges of theopposing faces of the glass sheets 1A, 1B. That is, microscopic gapswhich can act as passage for gas molecules tend to be formed at theinterfaces between the metal material 3 and the glass sheets 1A, 1B. Inparticular, such deterioration in the interfaces tend to occur fromexposed portions of the interfaces. In order to restrict this, the metalmaterial 3 and the glass sheets 1A, 1B should be bonded in such a mannerthat no stress concentration occur at the interfaces when an externalforce is applied to remove the metal material 3 and the glass sheets 1A,1B from each other. Accordingly, it is important that the bonding of themetal material 3 be effected including the edges of the opposing facesof the glass sheets 1A, 1B.

(Second Embodiment)

FIGS. 4 and 5 also are partial sections showing bonding portion usingthe metal material 3. In this case, the glass sheets 1A, 1B aresuperposed with the edge 5A of the lower glass sheet 1A projectingbeyond the edge 5B of the upper glass sheet 1B. Under this condition,the metal material 3 is charged between the opposing faces of the glasssheets 1A, 1B. In this manner, in the case of the construction of FIGS.4 and 5, the metal material 3 is charged over a constant width,including at least the edge 5B of the opposing face of the glass sheet1B.

(Third Embodiment)

In FIG. 6, a wire member 6 acting also as a spacer is disposed at thebonding portion between the two glass sheets 1A, 1B. This wire member 6is made of a different material from the metal material 3. This wiremember 6 is placed in contact with the metal material. Though the wiremember 6 is not directly involved in the bonding, a particular componentof this wire member is caused to be dissolved into the metal material 3,so that it can improve the bonding strength between the metal material 3and the glass sheets 1A, 1B.

(Fourth Embodiment)

FIG. 7 shows an embodiment in which the outer surface of the metalmaterial 3 is coated with a protecting coating film 7. This protectingcoating film 7 is provided for reducing the influence from theenvironment such as water on the metal material 3. An embodiment shownin FIG. 8 is similar to that of FIG. 7. In this case, however, theprotecting coating film 7 is provided to coat the entire section of theperipheral edge, so as to provide the protection of the sealed portionfrom the surrounding and also improvement of the strength.

In both of the embodiments of FIGS. 7 and 8, the protecting coating film7 may be formed of any material such as organic material such as aresin, or an inorganic material such as ceramics or metal material 3 aslong as it can fulfill the above-noted object. The air-tight sealingfunction per se is provided by the metal material 3. But, the protectingcoating film 7 plays an indirect role in effectively maintaining theair-tight sealing performance as a protective layer or reinforcing layerfor enhancing strength. Thus, such construction too is not contradictoryto the concept of the present invention.

(Fifth Embodiment)

FIGS. 9 and 10 are partial sections showing constructions out of thescope of the claims of the present invention. That is, as shown in FIG.9, metal coating films 8 are formed in advance on the opposing face ofthe two glass sheets 1A, 1B at the bonding portion so as to improve thewettability to the metal material 3. The metal material 3 is bonded tothese metal coating films 8, not forming direct bonding with thesurfaces of the glass sheets 1A, 1B. Further, in FIG. 10, layers ofmetal material 3 are formed in advance on the opposing faces of theglass sheets 1A, 1B at the portions thereof to be bonded and then theseglass sheets are placed in opposition to each other and heated and fusedto be attached to each other. In this case, there exist interface oxides9 at the overlapping portions of the layer surfaces.

These constructions shown in FIGS. 9 and 10 are not suitable formaintaining the high degree of air-tightness at the peripheral edge ofthe glass panel P. That is, although physical bonding is formed, thebonding between the metal material 3 and the glass sheets 1A, 1B is notdense, so that microscopic gaps which can act as passage for gasmolecules tend to be formed.

(Sixth Embodiment)

FIGS. 11 an 12 are schematic views illustrating a manufacturing methodof a glass panel P suitable as a first method of the present invention.FIG. 11 is a side view in section and FIG. 12 is a plan view. The moltenmetal material 3 (solder 3A) is fed via a guide 12 from a solder meltingbasin 11 to be charged into the periphery of the gap between the glasssheets 1A, 1B. The solder melting basin 11 and the guide 12 are providedas an integrated assembly, so that as this assembly is moved along theedges 1A, 1B of the glass sheets 1A, 1B while charging the solder 3A,the entire peripheral edge of the glass sheets is sealed. In this case,the guide 12 was moved at a rate of 50 mm/s.

(Seventh Embodiment)

FIGS. 13 and 14 are views schematically illustrating a furtherembodiment of a manufacturing method of the glass panel P suitable asthe first method of the present invention. FIG. 13 is a side view insection and FIG. 14 is a plan view. In this case, a rotary disc 13 isinserted into the gap. This rotary disc 13 is driven to rotate by meansof a driving motor 14 and is movable along the peripheral edge of theglass panel. This rotary disc 13 helps the molten solder 3A to bedispensed from the solder melting basin 11, so that the solder 3A ischarged to the peripheral edge of the gap between the glass sheets 1A,1B. And, this disc provides the function of physically renewing theinterfaces between the solder 3A and the glass sheets 1A, 1B. As this ismoved along the edges of the glass sheets 1A, 1B while charging thesolder 3A, the entire peripheral edges of the glass sheets are sealed.In this case, the rotary disc 13 was rotated at 2000 rpm clockwise asseen in the plan view of FIG. 14. The moving direction of the rotarydisc 13 in this case was in the direction of arrow shown in FIG. 14.

(Eighth Embodiment)

FIGS. 15 and 16 are schematic illustration of an embodiment relating tothe first method of the present invention. FIG. 15 is a side view insection and FIG. 16 is a plan view. Like the method shown in FIG. 11,the molten solder 3A from the melting basin 11 is charged via the guide12 into the peripheral edge of the gap between the glass sheets 1A, 1B.Further, in this embodiment, a rotary bar 15 is provided for physicallyrenewing the interfaces between the solder 3A and the glass sheets 1A,1B, so as to forcibly stir the charged solder 3A. This rotary bar 15 isrotatably driven by means of a driving motor 14. In FIG. 16, the guide12 and the rotary bar 15 advance in the direction of arrow. In thiscase, the rotary bar 15 was rotated clockwise as seen in a directionfrom which the glass panel P is seen from the side of the driving motor14. The rotational speed was set at 15000 rpm. The solder melting basin11 and the rotary bar 15 are moved together. Then, as they are movedalong the edges of the glass sheets 1A, 1B to charge the solder 3A, theentire peripheral edge of the glass sheets is sealed.

(Ninth Embodiment)

FIG. 17 illustrates a method of charging the metal material 3 into thegap of the peripheral edges of the glass sheets 1A, 1B by causing thematerial 3 to permeate into the gap by a capillary phenomenon. In doingso, the pair of glass sheets 1A, 1B are heated and maintained at atemperature below a liquidus temperature of the metal material 3. At thesame time, vibration is applied to at least one of the molten metalmaterial 3 and the glass sheets 1A, 1B.

The heating of the glass sheets 1A, 1B is effected by placing andheating them on a graphite plate of a hot plate device. And, as themetal material 3 is molten by using e.g. a ultrasonic soldering ironhaving a soldering end thereof vibrated at a predetermined frequency,the material is caused to permeate into the gap V between the glasssheets 1A, 1B. FIG. 17 illustrates a process for sequentially feedingthe wire member of the solder 3A as the metal material 3. After thesolder 3A has been permeated, it is cooled to the room temperature so asto seal the outer periphery of the glass sheets 1A, 1B.

(Tenth Embodiment)

FIG. 18 too shows a method of charging the metal material 3 into the gapat the peripheral edges of the glass sheets 1A, 1B by means ofpermeation thereof utilizing the capillary phenomenon. In this case too,the glass sheets 1A, 1B are heated and maintained at a temperature belowthe liquidus temperature of the metal material 3 and vibration isapplied to at least one of the metal material 3 and the glass sheets 1A,1B.

In this case, however, the solder 3A as the metal material 3 is moltenin advance and reserved in the solder melting basin 11. Then, anappropriate amount of the solder 3A is withdrawn and fed from the bottomof the solder melting basin 11. And, in this embodiment too, while thesolder 3A is maintained at this molten state by using e.g. a supersonicsoldering iron 10, the solder is caused to permeate into the gap Vbetween the glass sheets 1A, 1B.

(Other Embodiments)

Incidentally, the composition of the glass sheets 1A, 1B employed in therespective embodiments described above or any other embodiment is notparticularly limited. Any component such as of soda lime silica glassused in a standard window pane, borosilicate glass, aluminosilicateglass, crystallized glass, etc. may be employed. Further, themanufacturing method of the glass sheets 1A, 1B is not particularlylimited, as it can be any of float process, roll-out process, down-drawprocess, press process, etc. Further, it is also possible to employair-cooled tempered glass sheets 1A, 1B. Moreover, on the surfaces ofthe glass sheets 1A, 1B, oxide coating films, metal coating films may beformed for the purpose of improvement in the optical and/or thermalproperties. Unlike the metal coating films for solder fusion formed bymolten metal spraying or plating, these films, if formed as dense filmsby such process as thermal decomposition method, chemical vapordeposition method, sputtering process, etc, can be firmly bonded to thesurfaces of the glass sheets 1A, 1B to be integrated therewith.Therefore, the use of the glass sheets 1A, 1B having such coating filmsformed thereon is not contradictory to the essential concept of thepresent invention, that is, the direct bonding between the glass sheets1A, 1B and the metal material 3.

Further, it is also not contradictory to the essential concept of thepresent invention to employ a film which is physically or chemically soweak as not to interfere with the hermetic sealing between the glasssheets 1A, 1B and the metal material 3. For instance, it can be acoating film which is dissolved into the metal material 3 in the courseof the direct bonding between the glass sheets 1A, 1B and the metalmaterial 3 and which will hardly remain thereafter at the interfacesbetween the glass sheets 1A, 1B and the metal material 3.

Also, the use of the glass sheets 1A, 1B in the present invention arenot limited the use of the one glass sheet 1A and the other glass sheet1B having a same width or same dimensions. It is also possible to employglass sheets having different dimensions. And, the superposing manner ofthe two glass sheets 1A, 1B is not limited to superposing them withtheir edges in alignment with each other. Instead, the edge 5A of oneglass sheet 1A may project beyond the edge 5B of the other glass sheet1B. Further, the glass panel P may be assembled from one glass sheet 1Aand the other glass sheet 1B having different thickness from each other.

The glass panel P having hermetic sealed peripheral edge may be sealedwith its gap V depressurized by a known art, e.g. by the methoddisclosed in the Japanese national publication gazette No. Hei.5-501896. Or, an opening provided for evacuation depressurization may besealed by a method similar to the present invention. In either case, thepresent invention relates to the art of hermetic sealing of theperipheral edge of the glass panel P, the invention does not provide anylimit in the method of sealing the gap V under a depressurizedcondition.

Next, some examples will be described.

EXAMPLE 1

<Shape of Glass Panel>

A float glass sheet having thickness of 3 mm was cut into a square sheetof 300 mm×300 mm and a square sheet of 290 mm×290 mm, respectively. Inthe 290 mm square glass sheet, a through hole having a diameter of 2.0mm was formed at the center thereof. Then, these two glass sheets werewashed and dried.

Thereafter, the 300 mm square glass sheet was placed and on the upperside thereof, a plurality of pillars having a height of 0.05 mm and adiameter of 0.5 mm were arranged with a spacing of 20 mm from eachother; and the 290 mm square glass sheet with the through hole definedtherein was superposed thereon with the centers of the two glass sheetsbeing aligned with each other. The strain point of these glass sheetswas 500° C.

<Metal Material>

As the metal material, there was employed solder which was a lead-freesingle metal material having the composition of Sn 90.5%, Zn 9.0%, Ti0.15%, Cu 0.35%.

<Charging Operation of the Metal Material>

The two glass sheets were set on a graphite plate of a hot plate deviceand heated to 150° C. On the other hand, the solder was molten by meansof a ultrasonic soldering iron having its soldering end vibrated at thefrequency of 60 kHz.

By causing the molten solder to permeate into the gap between the twoglass sheets, the bonding portion was formed over the entire surface atthe peripheral edges of the opposing faces of the glass sheets. Thefeeding operation of the solder to the bonding portion was carried outby sequentially feeding a wire material of the solder of theabove-described composition. Incidentally, this solder had a liquidustemperature of 215° C. Thereafter, by cooling to the room temperature,the outer peripheral edge of the gap was sealed hermetically by means ofthe solder. With this there was obtained a glass panel in which thesolder was permeated to fill the gap between the two glass sheets andthe sealing width at the gap of the glass sheets from the peripheraledge ranged from 2.5 mm to 4 mm and the solder covered the entireperiphery of the side faces of the 290 mm square glass sheet. All ofthese operations were carried out in the atmosphere. Further, the solderwas permeated such that as shown in FIG. 17, the surface of the moltensolder was covered with a thin oxide layer while the inner portion ofthe solder permeating into the gap of the glass sheets did not containoxides. The cross section of this bonded portion was observed to findthat it was like the one shown in FIG. 5 over the entire periphery.

<Leak Test>

On this glass panel, air was forcibly evacuated from the gap through thethrough hole of 2.0 mm diameter to test leakage therefrom by means of ahelium leak detector. It was observed that the leak was less than1×10⁻¹¹ (Pa.m³/s) demonstrating the extremely high airtightness at theperipheral edge of this glass panel.

<Determination of Thermal Conductance>

Separately from the above, on this glass panel, the evacuation throughhole was sealed by means of evacuation in the same manner as theperipheral edge. At the time of sealing, the pressure inside the glasspanel was determined as being lower than 1×10⁻³ (Pa). Then, the thermalconductance of this glass panel was determined as 2.5 (W/m².K) (2.2(kcal/m²h° C.), demonstrating the glass panel having an extremely highheat insulating performance.

<Test of Elution of Lead>

Also, a test of lead elution was conducted in the manner described next.The sample glass panel was dipped into 2000 ml of pure water having atemperature of 80° C. and maintained therein for 24 hours. Then, thelead content of the liquid was determined by means of ICP spectrometry.From this content, it was tried to obtain an elution amount of lead perunit area at the portion of the bonded portion where the solder wasexposed. As a result, the lead concentration in the liquid was below thedetection limit, showing that no lead was eluted.

<Determination of Oxygen Content>

The solder was sampled from the bonded portion for analysis. It wasshown that the solder contained 0.0015% of O (oxygen).

Further, as the method of feeding the solder for bonding, the method ofFIG. 18 was employed, so that a solder meting basin was provided formelting the solder in advance and reserving it therein and anappropriate amount of the solder was fed from the bottom face of thebasin. With the other conditions than this method being the same asabove, a glass panel was obtained. This glass panel was evaluated in thesame manner as above and the same results were obtained.

Further, except for the height of the pillars changed to 0.2 mm, withthe other conditions being the same, a further glass panel was obtainedand the results of evaluation of this were also the same.

TABLE 1 example example example example Example Component 1 2 3 4 5 Sn90.5 99.85 99.5 90.5 98.5 Zn 9 0 0 9 0.5 Al 0 0 0 0 0.5 Si 0 0 0 0 0.5Ti 0.15 0.15 0.15 0.15 0.005 Cu 0.35 0 0.35 0 0 Total 100 100 100 100100 TL (° C.) 215 250 — — —

TABLE 2 example example example example Example Component 6 7 8 9 10 Sn98.5 0 90.8 99.65 98.5 Zn 0 95 9 0 0.5 Al 2 5 0.1 0.1 0.5 Si 0 0 0.1 0.20.5 Ti 0 0 0.002 0.05 0.006 Cu 0 0 0 0 0.01 Total 100 100 100 100 100 TL(° C.) 380 382 205 230 215

EXAMPLES 2-10

By using solder having the compositions shown in Tables 1 and 2 above,and with the other conditions being the same as those in example 1,glass panels were produced.

For all of the examples 2-10 shown in Tables 1 and 2, the same leaktests, determination of thermal conductance, the lead elution tests andthe determination of oxygen contents as example 1 were carried out.Then, substantially same results as the example 1 were obtained.

EXAMPLE 11

The glass panel used in this example had the same shape as that used inexample 1. In this case, however, a metal wire containing Ti and havinga diameter of 0.05 mm was disposed at the gap between the bondedportions of the glass sheets.

The two glass sheets were set on a graphite plate of a hot plate deviceand heated to 150° C. On the other hand, the solder as the single metalmaterial having the composition of Sn 91% and Zn 9.0% was molten bymeans of a ultrasonic soldering iron having its soldering end vibratedat the frequency of 60 kHz. By causing the molten solder to permeateinto the gap between the two glass sheets, the bonding portion wasformed over the entire surface at the peripheral edges of the opposingfaces of the glass sheets. In the course of this, the Ti-containingmetal wire was placed in contact with the molten solder. The feedingoperation of the solder to the bonding portion was carried out bysequentially feeding a wire material of the solder of theabove-described composition. Incidentally, this solder had a liquidustemperature of 198° C. Thereafter, by cooling to the room temperature,the outer peripheral edge of the gap was sealed hermetically by means ofthe solder. With this there was obtained glass panel in which the solderwas permeated to fill the gap between the two glass sheets and thesealing width at the gap of the glass sheets from the peripheral edgeranged from 2.5 mm to 4 mm and the solder covered the entire peripheryof the side faces of the 290 mm square glass sheet. All of theseoperations were carried out in the atmosphere. When the condition of thesection of this bonded portion was observed, it was same as shown inFIG. 5 over the entire periphery.

On this glass panel, the same leak test, determination of thermalconductance, and the lead elution test were carried out as example 1.Then, substantially same results as the example 1 were obtained.

Further, like the example 1, on the section at the bonded portionbetween the solder and the respective glass sheets, a line analysis anda mapping analysis were carried out by EPMA to check the distribution ofthe respective components of the solder. As a result, it was seen thatthe solder contained Ti which had been dissolved from the Ti-containingmetal wire and contained also oxygen.

EXAMPLE 12

In this example, when the molten solder was caused to permeate into thegap between the glass sheets by the capillary phenomenon, two kinds ofvibrations of 40 kHz and 700 Hz were applied simultaneously.Specifically, the 40 kHz vibration was applied to the soldering end ofthe ultrasonic soldering iron and the 700 Hz low-frequency vibration wasapplied to the entire ultrasonic soldering iron by means of anothervibrating member. The other conditions were same as in example 1. Inthis case, the sealing width of the gap from the edge was from 3.0 mm to3.6 mm. The uniformity of the sealing width was good. The evaluations ofthe glass panel produced were carried out in the same manners as theexample 1 and all the results were also same as the example 1.

EXAMPLE 13

In this example too, when the molten solder was caused to permeate intothe gap between the glass sheets by the capillary phenomenon, two kindsof vibrations of 40 kHz and 700 Hz were applied simultaneously. In thisexample, however, the 40 kHz vibration was applied to the soldering endof the ultrasonic soldering iron and the 700 Hz low-frequency vibrationwas applied to the peripheral edge of the upper glass sheet by means ofanother vibrating member. The other conditions were the same as theexample 1. In this case, the sealing width of the gap from the edge wasfrom 3.0 mm to 3.6 mm. The uniformity of the sealing width was good. Theevaluations of the glass panel produced were carried out in the samemanners as the example 1 and all the results were also same as theexample 1.

EXAMPLE 14

<Shape of Glass Panel>

The shape of the glass panel in this example was as follows. A floatglass sheet having thickness of 3 mm was cut into two square sheets of300 mm×300 mm. In one glass sheet, a through hole having a diameter of2.0 mm was formed at the center thereof. Then, these two glass sheetswere washed and dried.

Thereafter, one glass sheet was placed and on the upper side thereof, aplurality of pillars having a height of 0.2 mm and a diameter of 0.5 mmwere arranged with a spacing of 20 mm from each other; and the otherglass sheet with the through hole defined therein was superposed thereonwith the peripheral edges of the two glass sheets being aligned witheach other. The strain point of these glass sheets was 500° C.

<Metal Material>

As the bonding material, there was employed solder which was asubstantially lead-free single metal material having the composition ofSn 90.85%, Zn 9.0% and Ti 0.15%. The liquidus temperature of this solderwas 215° C.

<Heating Condition of the Glass Sheets>

Prior to the charging of the solder, the two glass sheets were set on agraphite plate of a hot plate device and were heated to 180° C.

<Charging Operation of the Metal Material>

The permeation of the metal material was carried out in the followingmanner. By the method schematically illustrated in FIG. 11, theperipheral edges of the two glass sheets were sealed. That is, into thegap between the heated glass sheets, the solder molten in the soldermelting basin was fed by the pipe having the guide, so that the solderwas charged into the gap between the glass sheets for bonding themtogether. The guide was a metal plate having a thickness of 0.15 mm, aportion of which was inserted from the leading end, i.e. the outlet, ofthe pipe slightly into the inside of the pipe and the gap. The pipe hadan inner diameter of 3 mm and the inserting depth of the guide into thegap was about 5 mm. While feeding the solder, this solder feeding devicewas moved along the peripheral edges, whereby the solder-charged portionwas formed over the entire peripheral edge of the gap. Thereafter, theassembly was cooled to the room temperature, so as to hermetically sealthe outer peripheral edges of the gap with the solder. The solder wascharged at the gap between the opposed glass sheets and the sealingwidth at this gap from the edge was about 5 mm. Incidentally, all theseoperations were carried out in the atmosphere. The solder fed was theportion of the solder which had not been exposed to the atmospherewithin the solder melting basin and which therefore did not containoxides.

On this glass panel, the same leak test, determination of thermalconductance, the lead elution test and the determination of oxygencontent were carried out as example 1. Then, substantially same resultsas the example 1 were obtained.

EXAMPLE 15

In this example, the shape of the glass panel, the metal material andthe heating condition of the glass panel were all the same as thoseemployed in example 14.

By the method schematically illustrated in FIG. 13, the peripheral edgesof the two glass sheets were sealed. That is, into the gap between theheated glass sheets, the solder molten in the solder melting basin wasfed by using a rotary disc acting as a guide and acting also as astimulus conducting member to be charged into the gap, thereby bondingthe glass sheets together. The rotary disc was a metal disc having athickness of 0.1 mm and a diameter of 20 mm. The rotary disc wasprovided at the outlet of the solder feeding device such that the discwas entirely submerged in the solder to be fed. This rotary disc has afunction of introducing the solder into the gap and a further functionof physically renewing the interface between the solder and the glasssheets.

In feeding the solder to the gap, the portion of the solder exposed tothe atmosphere is not to be fed. This is because such solder portionexposed to the atmosphere contains oxides. The rotary disc has a portionthereof inserted into the gap and the inserting depth from the edge ofthe glass sheet was about 3 mm. The rotation direction was clockwise asseen in a plan view of the glass panel as shown in FIG. 14 and itsmoving direction was the direction denoted with an arrow in FIG. 14. Therotational speed of the rotary disc was 2000 rpm.

By this method, while feeding the solder, this solder feeding device wasmoved along the peripheral edge to form a solder-charged portion overthe entire surface at the peripheral edges of the opposing faces of theglass sheets. Thereafter, the assembly was cooled back to the roomtemperature to hermetically seal the outer periphery of the gap with thesolder. The solder remained charged at the gap between the two glasssheets and the sealing width at this gap from the edge was about 3 mm.Incidentally, all these operations were carried out in the atmosphere.

On this glass panel, the same leak test, determination of thermalconductance, the lead elution test and the determination of oxygencontent were carried out as example 1. Then, substantially same resultsas the example 1 were obtained.

EXAMPLE 16

In this example, the shape of the glass panel, the metal material andthe heating condition of the glass panel were all the same as thoseemployed in example 14 and example 15.

By the method schematically illustrated in FIG. 15, the peripheral edgesof the two glass sheets were sealed. That is, into the gap between theheated glass sheets, the solder molten in the solder melting basin wasfed by using a pipe having a guide to be charged into the gap. In doingthis, the interface between the solder charged into the gap between thetwo glass sheets and the glass was being physically renewed by means ofa rotary bar acting as a stimulus conducting member, the two glasssheets were bonded together. As the rotary bar, there was employed ametal bar having a diameter of 0.15 mm. The solder melting basin and theguide and their functions are as same as those described in example 14.Although the solder was forcibly stirred by means of the rotary bar, therotary bar was adapted to immediately follow the guide so as to preventthe portion of the solder exposed to the atmosphere and containingoxides from entering the gap. The rotary bar had a portion thereofinserted into the gap and the inserting depth from the edge of the glasssheet was about 5 mm. By this method, while feeding the solder, thissolder feeding device was moved along the peripheral edge to form asolder-charged portion over the entire surface at the peripheral edgesof the opposing faces of the glass sheets. Thereafter, the assembly wascooled back to the room temperature to air-tightly seal the outerperiphery of the gap with the solder. The solder remained charged at thegap between the two glass sheets and the sealing width at this gap fromthe edge was about 5 mm. All these operations were carried out in theatmosphere. The solder fed was the solder portion which had not beenexposed to the atmosphere inside the solder melting basin and thereforedid not contain oxides.

On this glass panel, the same leak test, determination of thermaltransmission coefficient, the lead elution test and the determination ofoxygen content were carried out as example 1. Then, substantially sameresults as the example 1 were obtained.

Comparative Example 1

Solder having the composition of Pb 91.0%, Sn 5.0%, Zn 3.0%, Sb 1.0% wasemployed. With the other conditions being the same as example 1, a glasspanel was manufactured. In this case, however, the pre-heatingtemperature of the glass sheets was set at 200° C.

Leak was tested by means of a helium leak detector. It was observed thatthe leak was less than 1×10⁻¹¹ (Pa.m³/s) demonstrating the extremelyhigh airtightness at the peripheral edge of this glass panel. However,when a lead elution test was conducted in the same manner as example 1,it was observed that the elution amount of lead per unit area at theportion of the bonded portion where the solder was exposed was 0.4mg/cm², showing significant elution of lead.

Comparative Example 2

A float glass sheet having thickness of 3 mm was cut into two squaresheets of 300 mm×300 mm. In one glass sheet, a through hole having adiameter of 2.0 mm was formed at the center thereof. Then, these twoglass sheets were washed and dried.

Then, on each of these two glass sheets, along the entire peripheraledge of its one side, an electroless nickel plating was applied in thethickness of 0.2 μm by a standard method by a width of 10 mm from theedge of the respective glass sheet. Next, on the nickel plating of oneglass sheet, a foil of solder having the composition of Pb 91.0%, Sn5.0%, Zn 3.0% and Sb 1.0% was placed in the width of 10 mm and thethickness of 0.1 mm. Further, on the face of this glass sheet, aplurality of pillars having the height of 0.05 mm and the diameter of0.5 mm were arranged with a spacing of 20 mm from each other.

Thereafter, the other glass sheet having the through hole definedtherein was superposed on the one glass sheet, with the centers thereofbeing aligned with each other and also with the faces thereof with thenickel plating being in opposition to each other.

These two glass sheets were then set on a graphite plate and chargedinto an electric furnace which was maintained at 350° C. and kepttherein for 15-minutes for melting the solder foils so as to bond theentire peripheral edges of the opposing faces of the glass sheets.Thereafter, by cooling the assembly back to the room temperature, therewas obtained a glass panel having the outer periphery of the gap sealedwith the nickel plating and the solder foils.

On this glass panel, air was forcibly evacuated from the gap through thethrough hole of 2.0 mm diameter to test leakage therefrom by means of ahelium leak detector. It was observed that the leak amount was more than1×10⁻³ (Pa.m³/s) demonstrating insufficient airtightness at theperipheral edge of this glass panel. Further, when a lead elution testwas conducted in the same manner as example 1, it was observed that theelution amount of lead per unit area at the portion of the bondedportion where the solder was exposed was 0.4 mg/cm², showing significantelution of lead.

Comparative Example 3

A float glass sheet having thickness of 3 mm was cut into two squaresheets of 300 mm×300 mm. In one glass sheet, a through hole having adiameter of 2.0 mm was formed at the center thereof. Then, these twoglass sheets were washed and dried.

Then, on each of these two glass sheets, along the entire peripheraledge of its one side, paste of solder having the composition of Pb91.0%, Sn 5.0%, Zn 3.0% and Sb 1.0% was applied in the width of 10 mm asmeasured from the edge of the glass sheet. Then, by sintering at 350°C., a solder layer having the thickness of 0.15 mm was formed on theglass sheet. Further, on the face of this glass sheet, a plurality ofpillars having the height of 0.2 mm and the diameter of 0.5 mm werearranged with a spacing of 20 mm from each other.

The other glass sheet having the through hole defined therein was setover the one glass sheet with the centers of the glass sheets beingaligned with each other and the glass sheet faces thereof having thesolder layers being opposed to each other and these glass sheets wereplaced one on the other.

These two glass sheets were then set on a graphite plate and chargedinto an electric furnace which was maintained at 350° C. and kepttherein for 15 minutes for melting the solder layers so as to bond theentire peripheral edges of the opposing faces of the glass sheets.Thereafter, by cooling the assembly back to the room temperature, therewas obtained a glass panel having the outer periphery of the gap sealedwith the welded solder layer.

On this glass panel, the leak test and lead elution test were conducted.Then, substantially same results as comparison example 2 were obtained.

TABLE 3 Example Comparative Comparative Comparative Comparativecomponent 11 examples 1-3 example 4 example 5 example 6 Sn 91.0 5 11 2048 Zn 9 3 3 3 3 Pb 0 91 85 76 48 Sb 0 1 11 1 1 total 100 100 100 100 100TL (° C.) 380 297 286 266 210

Comparison Examples 4-6

By using the solder having compositions shown in Table 3 above, glasspanels were manufactured in the same manner as example 1. In thesecases, however, the preheating temperature of the glass sheets was 200°C. in the case of the comparative example 4 and the comparative example5 and 150° C. in the case of the comparative example 6. These soldercompositions are out of the claimed scope of the present invention.

On these manufactured glass panels, the leak tests were conducted. Then,substantially same results as the comparative example 2 were obtained.Observation of the portions of the glass sheets where the leak wasparticularly conspicuous revealed partial detachment of the solder.

The lead elution test conducted like example 1 revealed substantiallysame results as comparative example 2.

INDUSTRIAL APPLICABILITY

The glass panel and its manufacturing method of the present inventionfind their applications in the field of building construction, vehicles(window shield of automobile, railway train or of a boat), variousinstruments (display panel of a plasma display device, a door or wall ofa refrigerator or heat-insulating device), etc.

The composition of the glass sheets to be employed in the presentinvention is not particularly limited. Any composition used in thestandard window pane such as soda lime silica glass, borosilicate glass,aluminosilicate glass, crystallized glass, etc. can be used.

What is claimed is:
 1. A glass panel including a pair of glass sheets disposed in opposition to each other with forming a gap therebetween, peripheral edges of the glass sheets being bonded directly by a single-alloy metal material for sealing the gap hermetically, wherein that the panel satisfies the following relationship: 100≦T _(L)≦(T _(S) 100) where T_(L) is the liquidus temperature of the metal material in degrees Celsius and T_(S) is the strain point of the glass sheets in degrees Celsius.
 2. The glass panel according to claim 1, wherein the metal material contains not more than 0.1 wt. % or substantially zero wt. % of lead.
 3. The glass panel according to claim 1, wherein the metal material contains at least two components selected from the group consisting of Sn, Zn, Al, Si and Ti.
 4. The glass panel according to claim 1, wherein the metal material contains oxygen in the range from 0.0001 to 1.5 wt. %.
 5. The glass panel according to claim 1, wherein the pair of glass sheets have different dimensions so that one glass sheet is disposed in opposition to the other glass sheet with the one sheet projecting at a peripheral edge thereof by a width of 1 to 10 mm from each peripheral edge of the other sheet with the metal material being charged from the projecting portion of the one glass sheet into the gap between the glass sheets.
 6. The glass panel according to claim 1, wherein the gap is sealed so as to keep a depressurized condition.
 7. A method of manufacturing a glass panel comprising the steps of: disposing spacers between a pair of glass sheets so as to form a gap therebetween; charging a molten single-alloy metal material to the peripheral edges of the glass sheets the metal material satisfying the following relationship: 100≦T _(L)≦(T _(S)−100)  where T_(L) is the liquidus temperature of the metal material in degrees Celsius and T_(S) is the strain point of the glass sheets in degrees Celsius; and directly bonding the glass sheets and the metal material together so as to seal the gap hermetically.
 8. The method of manufacturing a glass panel according to claim 7, further comprising the steps of heating and maintaining the pair of glass sheets at a temperature below the liquidus temperature of the metal material, the molten metal material having a portion coming into contact with an atmosphere and a further portion not coming into contact with the atmosphere before the metal material is charged into the gap between the glass sheets and charging into the gap at the peripheral edge of the glass sheets only the portion of the metal material which did not come into contact with the atmosphere, while preventing the portion which came into contact with the atmosphere from being charged into the gap.
 9. The method of manufacturing a glass panel according to claim 7, wherein the step of charging the molten metal material into the gap between the glass sheets employs a guide for guiding the metal material to the gap, at least a portion of the guide being inserted into the gap.
 10. The method of manufacturing a glass panel according to claim 9, wherein the guide is a plate-like or bar-like guide.
 11. The manufacturing method of a glass panel according to claim 7, wherein the method employs a stimulus conducting member for providing a physical stimulus to the interface between the molten metal material and the glass sheet surface so as to promote the direct bonding therebetween, at least a portion of the stimulus conducting member being inserted into the gap.
 12. The manufacturing method of a glass panel according to claim 11, wherein the stimulus conducting member is a plate-like or bar-like member.
 13. The manufacturing method of a glass panel according to claim 11, wherein the physical stimulus for promoting the direct bonding is provided by mechanical movement of the stimulus conducting member.
 14. The method of manufacturing a glass panel according to claim 11, wherein that unevenness is provided on a surface of the stimulus conducting member.
 15. The manufacturing method of a glass panel according to claim 9, wherein the guide and/or the stimulus conducting member is moved along the gap.
 16. The manufacturing method of a glass panel according to claim 13, wherein said mechanical movement of the stimulus conducting member is either at least one of rotation and vibration.
 17. The manufacturing method of a glass panel according to claim 9, wherein that at least one of the guide and the stimulus conducting member is made of the metal material.
 18. The manufacturing method of a glass panel according to claim 11, wherein the guide and the stimulus conducting member are provided as a single member having the functions of both of them.
 19. The manufacturing method of a glass panel according to claim 9, wherein the pair of glass sheets have different dimensions from each other and one glass sheet is disposed in opposition to the other glass sheet with a peripheral edge of the former projecting from a peripheral edge of the latter by a width of 1 mm through 10 mm, and the metal material is charged from the projecting portion of the one glass sheet toward the gap by utilizing capillary phenomenon.
 20. The manufacturing method of a glass panel according to claim 9, wherein the pair of glass sheets are heated and maintained at a temperature below the liquidus temperature of the metal material and under this condition, vibration is applied to at least one of the molten metal material or the glass sheets, so as to cause the metal material to permeate and to be charged into the gap by utilizing capillary phenomenon.
 21. The manufacturing method of a glass panel according to claim 20, wherein the vibration includes two or more kinds of frequencies and either one or both of them is/are applied to at least one of the metal material and the glass sheets.
 22. The manufacturing method of a glass panel according to claim 21, wherein the two or more kinds of vibrations having different frequencies of either a low frequency of 1 Hz to 10 kHz or a ultrasonic frequency of 15 to 100 kHz.
 23. The manufacturing method of a glass panel according to claim 7, wherein the metal material contains not more than 0.1 wt. % or substantially zero wt. % of lead.
 24. The manufacturing method of a glass panel according to claim 7, wherein the metal material contains two or more kinds of components selected from a group consisting of Sn, Zn, Al, Si and Ti.
 25. The manufacturing method of a glass panel according to claim 7, wherein the metal material contains O (oxygen) in the range from 0.0001 to 1.5 wt. %.
 26. The manufacturing method of a glass panel according to claim 7, wherein the gap is sealed so as to keep a depressurized condition. 